In forming processes utilizing dies, and the like, it is often advantageous to sense or measure stress or strain experienced by the die during the knock-out of the part being formed. The knock-out tonnage, as it is called, associated with part ejection, may be used to monitor and diagnose the process being used (i.e., part phoscoating), and die conditions (i.e., in-process assessment of progressive wear, cracking or spalling). Signals relating to knock-out tonnage are typically also indicative of the level of, or need for, sufficient lubrication to maximize service life.
The proposition to utilize conventional sensors in dies used in forming processes is not always straightforward. In typical die-sets, for example, there are no convenient or suitable methods to locate load sensors on the ejecting anvil or along the centerline of the die, due to the moving parts and signal transmission requirements, or the substantiality of the required sensors. Furthermore, the sensors themselves in such environments are required to withstand the shock loads and vibrations which occur on the moving parts and along the centerline of the die for extended periods of time.
Accordingly, the need remains for an alternative method of measuring ejection force in the dies in forming processes, which can either withstand or avoid the need to experience ejection tonnage directly, but rather, utilize an alternative approach to calculate or estimate the forces involved.